The present invention is related to silicone fluids useful as hydraulic fluids and more particularly the present invention relates to a silicone fluid with or without additives added thereto which silicone fluid mixture may be used as a brake fluid.
At the present time, the most common type of hydraulic fluids and more particularly brake fluids that are sold commercially are glycol based polyether fluids. Such commercial brake fluids are operative at most temperatures that is experienced in hydraulic systems and particularly in the braking system of an automobile. However, recently it has been discovered that under periods of stress certain portions of the braking system of an automobile may be exposed to excessively high temperatures which results also in the brake fluid being exposed to these high temperatures. In some cases, it has been found that these high temperatures exceed the flash point of commercial brake fluids. In addition, it has been discovered that commercial brake fluids such as the glycol based polyether brake fluids are not as chemically stable and do not have as high a boiling point as well as chemical stability at high temperatures as would be desirable. Accordingly, automobile manufacturers as well as others have looked into the use of other types of fluids as hydraulic fluids and particularly as brake fluids in an automobile.
While it is conceivable that many types of hydraulic fluids can be used in automobiles which hydraulic fluids would have superior high temperature properties than that evidenced by the glycol based polyether fluids, a constant deterrent into the use of such superior hydraulic fluids has been the cost of manufacturing such fluids. Thus, it is highly desirable to discover a hydraulic fluid useful as a brake fluid which has superior high temperature properties, that is, has a high flash point, a very high boiling point and exceptionally good chemical stability at high temperatures.
Another undesirable property of the present commercial brake fluids is their hygroscopicity in that such brake fluids will absorb a large amount of moisture from the air. As a result of the absorption of such moisture from the air the resulting brake fluid becomes very viscous. It has been particularly noticed that commercial brake fluids with the amount of moisture that they absorb from the air will cause such brake fluids to have excessively high viscosities at low temperatures and particularly at temperatures such as, minus 40.degree. C, such that such brake fluids are not particularly desirable for use in arctic climates or in climates which experience exceptionally cold weather during parts of the year. Accordingly, it is highly desirable to develop a hydraulic fluid and particularly a silicone hydraulic brake fluid which will not be hygroscopic and which will have the proper viscosity at low temperatures and even at abnormally low temperatures.
Silicone fluids have been suggested for use as hydraulic fluids and more particularly as brake fluids. See, for instance, the patent applications of Frank J. Traver, Ser. No. 132,556, filed Apr. 8, 1971, now U.S. Pat. No. 3,725,287, Ser. No. 125,398, filed Mar. 17, 1971 now U.S. Pat. No. 3,859,321 and Ser. No. 125,397, filed Mar. 17, 1971 now abandoned. However, silicone fluids such as those suggested in the above patent applications were not found to be produced at the present time as economically as would be desired.
Accordingly, it is one object of the present invention to provide for a silicone fluid which can be used as a hydraulic fluid and more particularly can be used as a brake fluid in vehicles which silicone fluid can be produced economically.
It is another object of the present invention to provide a novel silicone fluid useful as a brake fluid in automobiles which silicone fluid is non-hygroscopic.
It is an additional object of the present invention to provide a silicone fluid useful as a brake fluid which silicone fluid has an exceptionally low viscosity at low temperatures particularly in combination with certain additives.
It is yet another object of the present invention to provide a silicone fluid useful as a brake fluid which silicone fluid has exceptionally superior high temperature properties such as, its boiling point, its flash point and its chemical stability at high temperatures, as compared to other commercial brake fluids or other silicone hydraulic fluids.
These and other objects of the present invention are accomplished by means of the silicone fluid and the various additives that may be added to it which are set forth below.
It should be understood that the present invention is not solely limited to a silicone fluid or fluids for use solely in the hydraulic system of the brake system of an automobile, but that the silicone fluid or fluids defined below are directed generally to be used as hydraulic fluid mixture for all types of hydraulic systems. More particularly, the silicone fluid and the silicone fluids mixture defined below are directed for being used in the hydraulic system of the brake system of a vehicle. This includes the brake system of all types of vehicles such as, passenger automobiles, trucks and etc.